Platform with cooling circuit

STATEMENT OF GOVERNMENT INTEREST

The subject matter described herein was made with government support under Contract No. N00019-02-C-3003 award by the Department of the Navy. The government of the United States of America may have rights to the subject matter described herein.

BACKGROUND

The present disclosure is directed to a turbine engine component having a platform with a cooling circuit and a process for forming same.

Currently, a high level of cooling technology for turbine airfoil platforms involves the placement of a miniature core within the wall of the platform. This core is suspended between the hot side of the wall, or gas path, and the cold side of the wall. This technology pulls air from the cold non-gas path side through a number of cooling fins, i.e. trip strips protruding from the gas path side, and pins or pedestals spanning between the hot and cold walls. The air is evacuated out onto the gas path surface where the air spreads out on the surface to create a thin film of cooler air to help further protect the surface from hot gas path air.

<figref idrefs="DRAWINGS">FIG. 1</figref> illustrates a turbine vane <b>10</b> with a platform cavity <b>12</b> which has been formed using a core <b>14</b> (see <figref idrefs="DRAWINGS">FIG. 2</figref>). The vane has outer <b>16</b> and inner <b>18</b> platforms, with an airfoil <b>20</b> spanning there between. The airfoil <b>20</b> has multiple internal cavities <b>22</b> and <b>24</b> and has a pressure or concave side <b>26</b> and a suction or convex side <b>28</b>. The outer and inner platforms <b>16</b> and <b>18</b> respectively both have a hot gas path side <b>30</b> and a cooler non-gas path side <b>32</b>. The outer platform <b>16</b> has a platform cavity <b>12</b> whose entrance <b>34</b> allows the cooler air on the non-gas path side <b>32</b> to enter the cavity <b>12</b> and flow through the cavity <b>12</b> to exit onto the hot gas path side <b>30</b> of the outer platform <b>16</b> where this air creates a thin film of cooler air on the surface which protects that surface from the hot gas path air.

<figref idrefs="DRAWINGS">FIG. 2</figref> shows a cut away of the outer platform <b>16</b> prior to the cores <b>36</b> and <b>38</b> which form the airfoil cavities <b>22</b> and <b>24</b> being leached out. Also shown in the figure is the core <b>14</b>, prior to it being leached out. The core <b>14</b> has holes <b>40</b> of varying shape in it that helps create turbulent air flow within the cavity and increase surface area thereby increasing the heat transfer capability of the air.

<figref idrefs="DRAWINGS">FIG. 3</figref> shows a cut away of the outer platform <b>16</b> after the cores <b>36</b> ad <b>38</b> have been leached out of the airfoil to form the airfoil cavities <b>22</b> and <b>24</b>. The figure also shows the cavity <b>12</b> which is formed by the core <b>14</b> after it has been leached out. When the platform core <b>14</b> is leached out, the holes <b>40</b> in the core <b>14</b> leave a three dimensional mirror solid behind in the form of a plurality of pedestals <b>42</b>. Also trenches in the core <b>14</b> create trip strips <b>44</b> to further increase the turbulence of the air and increase the surface area, thereby increasing heat transfer.

<figref idrefs="DRAWINGS">FIG. 4</figref> shows a close up of the cut away of the cavity <b>12</b> in the outer platform <b>16</b> and shows the arduous paths <b>46</b> the air must travel from the entrance <b>34</b> of the cavity to the exit <b>48</b> on the gas path side of the platform.

This technology works extraordinarily well; however, it is complicated to implement in turbine vanes. It requires a four piece wax assembly for a turbine doublet which is not production friendly. The technology is expensive.

SUMMARY

An inexpensive approach to forming a turbine engine component with a platform cavity is described herein.

In accordance with the present disclosure, a turbine engine component broadly comprises an airfoil portion, said airfoil portion being bounded by a platform at one end, said platform having an as-cast open cavity bordered by at least one as-cast landing, and a plate welded to said at least one as-cast landing to cover said as-cast open cavity.

Further in accordance with the present disclosure, there is provided a process for forming a turbine engine component comprising the steps of casting a turbine engine component having an airfoil portion with a pressure side and a suction side and a platform with an open cavity and a landing positioned on a periphery of said cavity, positioning a plate over an opening in said open cavity, and welding said plate to said landing to close said cavity.

Other details of the platform with cooling circuit are set forth in the following detailed description in which like reference numerals depict like elements.

BRIEF DESCRIPTION OF THE DRAWINGS

<figref idrefs="DRAWINGS">FIG. 1</figref> illustrates a turbine vane with a cast in platform cavity;

<figref idrefs="DRAWINGS">FIG. 2</figref> illustrates a section view of an outer platform of the turbine vane of <figref idrefs="DRAWINGS">FIG. 1</figref> with the casting cores being present;

<figref idrefs="DRAWINGS">FIG. 3</figref> illustrates a section view of the outer platform of <figref idrefs="DRAWINGS">FIG. 1</figref> with the casting cores removed;

<figref idrefs="DRAWINGS">FIG. 4</figref> is an enlarged view of the outer platform cavity of <figref idrefs="DRAWINGS">FIG. 1</figref>;

<figref idrefs="DRAWINGS">FIG. 5</figref> illustrates a turbine vane with a covered platform cavity in accordance with the present disclosure;

<figref idrefs="DRAWINGS">FIG. 6</figref> is a sectional view of the outer platform prior to removal of the cores for forming internal cavities within the airfoil portion;

<figref idrefs="DRAWINGS">FIG. 7</figref> is a sectional view of the outer platform after the cores have been removed.

<figref idrefs="DRAWINGS">FIG. 8</figref> is a sectional view taken along lines <b>8</b>-<b>8</b> in <figref idrefs="DRAWINGS">FIG. 7</figref>;

<figref idrefs="DRAWINGS">FIG. 9</figref> is an enlarged view of the platform cavity; and

<figref idrefs="DRAWINGS">FIG. 10</figref> is a sectional view of an outer platform with a forward flowing cavity.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring now to <figref idrefs="DRAWINGS">FIG. 5</figref>, there is shown a turbine vane <b>100</b> with a covered platform cavity <b>102</b>. The vane <b>100</b> has outer <b>104</b> and inner <b>106</b> platforms with an airfoil <b>108</b> spanning between them. The airfoil <b>108</b> has multiple internal cavities <b>110</b> and <b>112</b> and has both a pressure or concave side <b>114</b> and a suction or convex side <b>116</b>. The outer and inner platforms <b>104</b> and <b>106</b> respectively have both a hot gas path side <b>118</b> and a cooler non-gas path side <b>120</b>. The outer platform <b>104</b> has a platform cavity <b>102</b> which is formed by welding a plate <b>122</b> onto the vane <b>100</b>. The entrance <b>124</b> to the cavity <b>102</b> is a hole extending through the plate <b>122</b>. This hole allows the cooler air on the non-gas path side <b>120</b> to enter the platform cavity <b>102</b> and flow through the cavity <b>102</b> to exit onto the hot gas path side <b>118</b> of the outer platform <b>104</b> where this air creates a thin film of cooler air on the surface which protects that surface from the hot gas path air.

<figref idrefs="DRAWINGS">FIG. 6</figref> shows a cut away of the outer platform <b>104</b> prior to the cores <b>130</b> and <b>132</b> which form the internal cavities <b>110</b> and <b>112</b> being leached out. The figure also shows the as-cast, open platform cavity <b>102</b> prior to having the cover or plate <b>122</b> being welded on. The as-cast platform cavity <b>102</b> may be located in proximity to the internal cavities <b>110</b> and <b>112</b> and adjacent the pressure side <b>114</b> of the airfoil <b>108</b>. The open platform cavity <b>102</b> includes a plurality of as-cast, integrally formed protuberances <b>134</b> and at least one as-cast, integrally formed trip strip <b>136</b>, which when air is run from one end of the cavity <b>102</b> to the other will increase air turbulence and surface area, thereby cooling the platform <b>104</b>. The as cast platform <b>104</b> also includes an entrance area <b>138</b> and an exit area <b>140</b> which is devoid of any such protuberances. The protuberances <b>134</b> can take the form of circular or oblong conics.

<figref idrefs="DRAWINGS">FIGS. 7 and 8</figref> show cut away views of the outer platform <b>104</b> after the airfoil cores <b>130</b> and <b>132</b> have been leached out of the airfoil to form the airfoil cavities <b>110</b> and <b>112</b>. The figures also show the cavity <b>102</b> formed by the casting and the welded on plate <b>122</b>. The welded plate <b>122</b> is welded onto the as-cast landing <b>142</b> which may be positioned on a periphery of the cavity <b>102</b> and which circumscribes the cavity <b>102</b>. As can be seen in <figref idrefs="DRAWINGS">FIG. 8</figref>, the plate <b>122</b> when welded into position rests on the protrusions <b>134</b> to create flow channels through the protrusions. The plate <b>122</b> when welded in position also rests on the landing <b>142</b>. Any suitable technique known in the art may be used to weld the plate <b>122</b> in position and to a wall of the cast platform <b>104</b>.

The hole <b>124</b> in the plate <b>122</b> is positioned over an entrance area <b>138</b> of the casting <b>145</b>. The hole <b>124</b> allows cooling fluid from the non-hot gas side of the platform <b>104</b> to enter the cavity <b>102</b>. Holes <b>146</b> are drilled into or otherwise formed in the exit area <b>140</b> of the cavity <b>102</b> so that the air can flow out of the cavity <b>102</b> into the hot air gas path. <figref idrefs="DRAWINGS">FIG. 9</figref> shows the arduous paths <b>144</b> the air must travel from the entrance <b>124</b> of the cavity to the holes <b>146</b> to exit onto the gas path side of the platform <b>104</b>. It should be noted that the plate <b>122</b> does not add any appreciable structural member to the platform <b>104</b> as its cored counterpart.

As can be seen from <figref idrefs="DRAWINGS">FIG. 9</figref>, the airfoil <b>108</b> has a chord line <b>150</b>. The cavity <b>102</b> may be located on either the pressure side or the suction side of the chord line <b>150</b>.

The process for forming the turbine engine component involves positioning the cores <b>130</b> and <b>132</b> in a mold (not shown). The turbine engine component <b>100</b> is then formed by a casting technique wherein molten metal is poured into the mold (not shown). As a result of the casting process and subsequent solidification of the molten metal, there is formed a component <b>100</b> having the airfoil <b>108</b> with the pressure side <b>114</b> and the suction side <b>116</b>, the platforms <b>104</b> and <b>106</b>, the open cavity <b>102</b> in the platform <b>104</b>, the protrusions <b>134</b>, the at least one trip strip, <b>136</b>, the entrance area <b>138</b>, the exit area <b>140</b>, and the peripheral landing <b>142</b>. Following solidification, the cores <b>130</b> and <b>132</b> may be removed using any suitable technique, such as leaching, known in the art. The plate <b>122</b> may then be attached to the outer platform <b>104</b> using any suitable welding or brazing technique known in the art. The exit holes <b>146</b> may be formed either before or after the plate <b>122</b> is installed. The exit holes may be formed using a drilling technique such as EDM.

One significant advantage to the technique described herein is that it is inexpensive. Another advantage is that while the entrance <b>124</b> may be located at the leading edge of the cavity <b>102</b> and the exit holes <b>146</b> may be located at the trailing edge of the cavity <b>102</b>, it is entirely feasible to reverse the structure as shown in <figref idrefs="DRAWINGS">FIG. 10</figref>. This means that the same air which is used to cool the back side of the platform <b>104</b> flowing forward can be used to create a protective cooling air film on the gas path side flowing aftward over the same region. This reverse flow is not possible using a mini core configuration due to the shape of the exits. The present technique may provide a distinct advantage in areas that can not be cooled by enhanced back side cooling alone.

There has been provided in accordance with the present disclosure a platform with a cooling circuit. While the present disclosure has been made in the context of one or more embodiments, it should be apparent that unforeseen alternatives, modifications, and variations may become apparent to those skilled in the art having read the foregoing description. It is therefore intended to embrace those alternatives, modifications, and variations as fall within the broad scope of the appended claims.